# The current in a coil varies with time t as $\mathrm{I}$ $=$ $3{\mathrm{t}}^{2}+$ $2\mathrm{t}$. If the inductance of coil be 10 mH, the value of induced e.m.f. at $$t=2~\mathrm{s}$$ will be: 1. $$0.14~\mathrm{V}$$ 2. $$0.12~\mathrm{V}$$ 3. $$0.11~\mathrm{V}$$ 4. $$0.13~\mathrm{V}$$

Subtopic:  Faraday's Law & Lenz Law |
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A coil of a mean area of 500 $c{m}^{2}$ and 1000 turns is held perpendicular to a uniform field of 0.4 Gauss. The coil is turned through $180°$ in $\frac{1}{10}$ seconds. The average induced e.m.f. is:

 1 0.04 V 2 0.4 V 3 4 V 4 0.004 V
Subtopic:  Faraday's Law & Lenz Law |
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The network shown in figure is a part of a complete circuit. If at a certain instant, the current 'i' is 10 A and is increasing at the rate of $4×{10}^{3}$ A/sec, then ${V}_{A}-{V}_{B}$ is:

 1 6 V 2 -6 V 3 10 V 4 -10 V
Subtopic:  LR circuit |
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A coil having an area ${A}_{0}$ is placed in a magnetic field which changes from ${B}_{0}$ $to$ $4{B}_{0}$ in time interval t. The average EMF induced in the coil will be:

1. $\frac{3{A}_{0}{B}_{0}}{t}$

2. $\frac{4{A}_{0}{B}_{0}}{t}$

3. $\frac{3{B}_{0}}{{A}_{0}t}$

4. $\frac{4{B}_{0}}{{A}_{0}t}$

Subtopic:  Faraday's Law & Lenz Law |
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From NCERT
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A rod AB of length l is moving with constant speed v in a uniform magnetic field on a conducting U-shaped wire as shown. If the rate of loss of heat energy across resistance R is Q, then the force needed parallel to velocity to keep rod moving with constant speed v is:

1.  Qv

2.  $\frac{\mathrm{Q}}{\mathrm{v}}$

3.  $\frac{{\mathrm{Q}}^{2}}{\mathrm{v}}$

4.  ${\mathrm{Q}}^{2}\mathrm{v}$

Subtopic:  Motional emf |
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A coil has 1,000 turns and 500 ${\mathrm{cm}}^{2}$ as its area. The plane of the coil is placed at right angles to a magnetic field of $2×{10}^{-5}$ $Wb/{m}^{2}$. The coil is rotated through  $$180^{0}$$  in 0.2 seconds. The average e.m.f. induced in the coil, in milli-volts, is:

 1 5 2 10 3 15 4 20
Subtopic:  Faraday's Law & Lenz Law |
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An electric potential difference will be induced between the ends of the conductor shown in the diagram when the conductor moves in the direction of:

1. P
2. Q
3. L
4. M

Subtopic:  Motional emf |
70%
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In a circuit with a coil of resistance 2 ohms, the magnetic flux changes from 2.0 Wb to 10.0 Wb in 0.2 second. The charge that flows in the coil during this time is:
1. 5.0 coulomb
2. 4.0 coulomb
3. 1.0 coulomb
4. 0.8 coulomb

Subtopic:  Faraday's Law & Lenz Law |
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A long solenoid of diameter 0.1 m has 2$×{10}^{4}$ turns per meter. At the centre of the solenoid, a coil of 100 turns and a radius of 0.01 m is placed with its axis coinciding with the solenoid's axis.  The current in the solenoid reduces at a constant rate from 0 A to 4 A in 0.05 s. If the resistance of the coil is , the total charge flowing through the coil during this time is:

1. 32$\mathrm{\pi \mu C}$

2. 16 $\mu C$

3. 32 $\mu C$

4. 16$\mathrm{\pi \mu C}$

Subtopic:  Mutual Inductance |
59%
From NCERT
NEET - 2017
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A conducting square frame of side 'a' and a long straight wire carrying current i are located in the same plane as shown in the figure. The frame moves to the right with a constant velocity v. The emf induced in the frame will be proportional to:

1. 1/x2
2. 1/(2x-a)2
3. 1/(2x+a)2
4. 1/(2x-a) x (2x+a)

Subtopic:  Motional emf |
71%
From NCERT
NEET - 2015
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